1. Field of the Invention
The present invention relates to an armature winding machine, and more particularly, an armature winding machine employing a piezoelectric excitation device for greater slot conductor cross-section yields by virtue of an induced vibration.
2. Background Art
The power obtainable or efficiency from an electric motor depends in part upon the cross-sectional area of the conductive wires located in the coil receiving slots of the motor's armature. Usually, the power obtainable may be optimized for an armature having coil receiving slots of a given cross-section by maximizing the percentage of the cross-section area of the slot that is filled with conductor. Accordingly, the present invention is concerned with an armature winding machine that utilizes a specialized technique to maximize the "slot fill" or cross-sectional area of conductive wire in the coil receiving slots of the armature being wound.
Experience has shown that the maximum slot fill (that is the cross-sectional area of conductive wiring within a slot divided by the cross-sectional area of the slot available to receive wire) has been found to be approximately 55%, with the remaining 45% of the slot cross-section area filled by gaps inherently caused by the wire and slot shapes. Armatures typically wound by fly winders have a slot fill sometimes as low as 40%. In some cases it has been found possible to achieve a slot fill in the order of 46% to 47% by exercising great care in the construction of the tooling. This high slot fill, while being highly desirable, is partly dependent upon the overall design of the armature.
The principle employed in the present invention wherein a vibratory technique is utilized to cause wires as being wound in a coil winding machine against armatures to seek the lowest level within armature slots can be understood by the following simple experiment: Into an empty cylindrical oatmeal container resting on a table, Rice Krispies.RTM. or similar dry cereal may be poured to a level even with the top of the carton. It is important that the container not be disturbed or shaken during the filling. Next, a top will be placed on the carton and then manually shaking the carton up and down striking the bottom of the container on the table for two or three dozen cycles.
At this time, if the top were removed, it would be easy to observe the Rice Krispies level would have lowered to a depth substantially below the starting level of the carton. It can be seen that before impacting or vibration, the carton was 100% full, but after impacting, was reduced to only 91% full, thus providing more room in the carton for additional Rice Krispies.
A search of the background art directed to the subject matter of the present invention conducted in the U.S. Patent and Trademark Office disclosed the following U.S. Letters Patent:
U.S. Pat. No. 4,027,827 issued Jun. 7, 1977 discloses connecting wires between armatures wound by an automatic armature winding machine clamped adjacent to commutator tangs with the finished wires hooked to the tangs of the wound armatures and the start wires looped about selected tangs of the armatures about to be wound.
U.S. Pat. No. 4,052,783 issued Oct. 11, 1977 teaches a technique for winding an armature and a shaft supporting core and a commutator having peripherally spaced tangs. The wire coils extend about a member supported for movement, when the member moves for twisting the wire to form a twisted wire loop on the member and transferring the twisted wire loop from the members to one of the tangs. The above steps are repeated to form a plurality of wire coils continuously interconnected by lead wires, each having a twisted wire loop connection with a corresponding tang.
U.S. Pat. No. 4,459,742 issued Jul. 17, 1984 discloses an armature winding machine method whose purpose is to increase the slot fill of the armatures wound on a flyer type armature winding machine of the type having inner and outer commutator shields. A tamper assembly is provided for engaging the coil ends immediately after they are wound. The tamper assembly is actuated by pushing tamper rods into engagement with coil ends. Thus, the coil sides would be pushed to locations more centrally of and deeper into the coil receiving slots than previously found available.
U.S. Pat. No. 5,377,893 issued Jan. 3, 1995 discloses an ultrasonic tape guide device wherein a video tape recorder employs fixed tape guides. These are activated ultrasonically by a piezoelectric ultrasonic vibrator to provide reduction in the amount of friction provided to a video tape crossing over the stationary fixed video tape guides.
A thorough review of the above-identified patents has concluded that none are believed to claim, teach, or disclose the particular novel combination of elements or functions set forth in the present invention. All of the cited patents are for different purposes or environments. Accordingly, it is the object of the present invention to provide an improved armature winding machine that greatly increases the amount of slot fill in armatures during the winding process.